1. Field of the Invention
The invention generally relates to machinery for manufacturing cables and other conductors and, more specifically, to an apparatus for applying soft filaments to continuous elongate articles.
2. Description of the Prior Art
In the manufacture of conductors and cables it is frequently necessary to apply elongate filaments to one or more continuous elongate elements. For example, in the manufacture of optical cables, a bundle of optical fibers are frequently moved through an application station at which a plurality of filaments are typically applied to or introduced into the bundle prior to being brought to an extrusion station at which an outer plastic covering or jacket is applied to encapsulate and shield the optical fibers. The elongate filaments that are introduced may be, for example, a bundle of very soft and flexible strands or fibers. Such filaments, while very soft and flexible, are extremely strong in tension and may be used, with or without additional rigid cores, in order to eliminate or minimize tension and, therefore, stretching of the optical fibers, the optical and electrical properties of which are very sensitive to tension. One of the problems that has been encountered is efficiently applying or introducing such Kevlar filaments into the cable. One specific example of such an optical cable has a "tight coated" construction, in which a plastic buffer is extruded directly onto the coated fibers to form a buffered fiber. While there are many different variations of such cable design, in a simplex structure, one or two light buffered fibers are surrounded with aramid yarn strength members and with a plastic jacket. However, one of the problems with introducing the aramid yarn filaments into the cable has been the difficulty of controlling and handling the filaments, particularly under higher speed conditions. Such filaments are typically very soft, flexible, lightweight and flimsy. Once unwound from a cop, a cylindrical or conical mass of such filamentary material wound on a quill or tube, the removed filament is very much subject to the forces that manifest themselves in such machine, including gravity, centrifugal force, and air turbulence. When the optical fibers are passed along the machine axis at the application station and the wound packages of filamentary materials are rotated about the machine axis and about the cable into which the filament is to be introduced, it has been found that above relatively low threshold rotational speeds it becomes very difficult, if not impossible, to control the filamentary material of the type under discussion, particularly the softer and flimsier forms of such filaments. Depending on the nature of the filamentary materials used, such threshold rotational speeds can be in the range of 100-150 rpm. At higher speeds, any such filamentary materials which fly off the wound packages or cops are extremely difficult to control and turbulence makes it very difficult to control the filaments, in some cases causing the filament to engage and snag the machine parts, become twisted and possibly even knotted, rendering the filament difficult to use and subject to damage. Such difficulties may necessitate the stopping of the applicator, resulting in down time and unnecessary loss of efficiency of operation.